The present invention relates to subminiature transformers and particularly to gapless subminiature transformers.
Conventional subminiature transformers are formed with a laminated core wherein each of the laminations is split to permit its insertion into a bobbin. The result of the split laminations, however, results in a breaking of the magnetic circuit causing inductance losses.
For studio grade audio applications, as well as certain computer applications, navigational devices, aircraft instrumentation, and the like, the inductance loss caused by the gaps in the laminations of a conventional subminiature transformer cannot be tolerated since the loss of inductance because of the air gap results in transformers having excessive leakage inductance, increased capacitance and increased resistance. As a result, various attempts have heretofore been made to provide a subminiature transformer having a gapless laminated core.
In one such prior art attempt, the windings of the transformer are toroidal. Such toroidal windings, however, do not lend themselves to uniform wire distribution and repeatability of manufacture. In addition, toroidal windings cannot readily be effected on automatic equipment. In addition, it is extremely difficult to obtain a toroidal winding with ultrafine wire (i.e., such as No. 52 wire which has a diameter on the order of 0.9 mil).
In another prior art attempt to solve the above problem, the bobbin is formed of two pieces which are assembled about the laminated core. That is, the bobbin is assembled about the laminations after the laminations are formed into a core stack. The major problem with this type of construction is that it is extremely difficult to bring the ultrafine wires of the transformer windings to the outside for interconnections.